The main objective of this study is to evaluate the effects of two diets with different glycemic index and fibre content on glucose metabolism and plasma lipid profile of 80 adolescents in 4 European centres.

Secondary objectives are to evaluate the effects of the two standardized diets on selected hormones and variables linked to inflammatory status.

Inclusion Criteria:

• Age 13-16 yrs
• Written informed consent
• Menstrual cycle for at least 6 months
• Overweight

Exclusion Criteria:

• Taking part simultaneously in another research trial
• Involvement in physical training (>4 h/week of vigorous physical activity)
• Any dietary treatment in the previous two months
• Body weight changes > 3 kg in the previous two months
• Gastrointestinal diseases, irritable bowel syndrome, or positive history for recurrent gastrointestinal symptoms such as nausea, vomiting, bloating, epigastric pain, abdominal pain, abdominal discomfort, flatulence, severe constipation
• Kidney diseases
• Type 1 or type 2 diabetes
• Thyroid or other hormonal diseases
• Other secondary causes (including illnesses) of hyperlipidemia or altered glucose metabolism
• Severe hyperlipidemia (total cholesterol > 300 mg/dL or triglycerides >300 mg/dL)
• Severe hypertension
• Positive history for eating disorders
• Any regular drug treatment
• Any food allergy and intolerance